There are a number of communications systems utilizing assigned frequency channels for use in a wireless RF telecommunications systems. These systems include the well known mobile or cellular telephone systems and the wireless RF telephone system between a base station and a number of subscriber units as described in U.S. Pat. 4,675,863. Since the number of communications channels set by the Federal Communications Commission is limited, and the demand for these frequencies continues to rise, new methods must be developed to increase the capacity of these limited number of channels. As user density increases, the usable frequencies near their information carrying capacity limit and the occurrences of RF interference increase.
There have been several systems employed to minimize the RF interference between various base stations and their respective portable units. One of these solutions utilizes a corner illuminated cellular array and places a sector antenna at every second corner of a hexagonally-shaped sector or cell. The antennas are situated so that they illuminate the cell inwardly from their respective corners.
Another solution, disclosed in U.S. Pat. No. 4,128,740, issued Dec. 5, 1978, uses a similar hexagonally-shaped cell arrangement with seven antennas at the center of each cell. Each cell uses a group of frequencies, which is different than the group of frequencies used by each surrounding cell. The cells are then arranged in such a manner so is to minimize co-channel and adjacent channel interferences. Both of the aforementioned systems require an excessive number of antenna sites and a large number of antennas.